1. Field of the Invention
The present invention relates to a communication system which is arranged by connecting plural repeating installations connected with one or more node terminals via a data transmission line and exchange data between the node terminals, between the repeating installations or between the node terminals and repeating installations, more specifically, for example, relates to a communication method and communication system which can securely transmit communication data from an originating source node terminal to a specified destination node terminal without reducing a data transmission amount per unit time.
2. Description of the Related Art
A communication system, which is arranged such that plural repeating installations respectively connected with one or more node terminals are connected with each other via a data transmission line and exchanges data between the node terminals, between the repeating installations or between the node terminals and repeating installations, has been generally known.
In the aforementioned conventional communication system, as communication path management which is used when communication data are transmitted from an originating source node terminal to a destination node terminal, for example, central managing method using a central managing device is generally adopted.
As for the central managing method, the central managing device connected with the communication system always monitors use/free state of plural data channels provided respectively to the repeating installations. At this time, for example, when a certain node terminal connected with a certain repeating installation makes a request of transmission of communication data, accordingly the repeating installation sends use request of data channels to the central managing device. The central managing device successively searches plural communication paths from an originating source node terminal to a destination node terminal for data channels in free state or in free-enabled state, and allocates the searched data channel to the repeating installation sending use request. As a result, communication paths from the originating source node terminal to the destination node terminal are secured, and communication data can be transmitted securely from the originating source node terminal to the destination node terminal along the communication paths.
However, according to the aforementioned central managing method of managing communication paths in the conventional communication system, for example, in the case where data are exchanged between the node terminals, every time a certain node terminal connected with a certain repeating installation make a request of transmission of communication data, the repeating installation connected with this node terminal transmits use request of data channels to the central managing device. Accordingly the central managing device successively searches plural communication paths from the originating node terminal to the destination node terminal for data channels in free state or in free-enabled state, and allocates the searched data channels to the repeating installation which made use request. Since the central managing device should perform such a complicated process, time required for securing the usable communication paths becomes comparatively longer. Therefore, there arises a problem to be solved such that it is difficult to increase a data transmission amount per unit time in the communication system.